API PS-6-Fuel and 12 other hydrocarbon materials were administered by gavage to groups of 10 male Fischer 344 rats five days per week for four weeks. A dose level of 2.0 g/kg was used for each material. The dose level was approximate since doses throughout the study were calculated based on the initial body weight of each animal. In addition, a negative control group received 2.0 g/kg of saline during each phase. Animals were observed twice daily for mortality and clinical signs of toxicity; body weights were recorded at initiation and at the time of scheduled sacrifice. The potential nephro-toxic effects of the test articles were assessed through gross and microscopic pathology evaluations. 2, 2, 7, 7-Tetramethyloctaine could not be tested due to the insolubility of the compound. No deaths occurred in either the API-6-Fuel or the saline-treated groups. One rat treated with 3-Methyloctane died on Day 10. Three rats died in the Octaine-treated group, one on Day 10 and two on Day 22. No antemortem observations were noted. No significant test material-related clinical signs were observed during the study. A decrease in body weight at terminal sacrifice was seen in all groups except the 2, 2, 4, 4, 5, 5, 7, 7-Octamethyloctane treated group. The decrease in the Decane group was numerically lower. The most pronounced decrease was seen in the API PS-6-Fuel and 2, 2, 3,-Trimethyloctane treated groups.